Coke oven gas naphthalene absorbing final cooler



COKE OVEN GAS NAPHTHALENE ABSORBING FINAL COOLER Filed Jan. 22, 1959Oct. 18, 1960 E. v. scHULTE ET AL 2 Sheets-Sheet 1 Oct. 18, 1960 E VSCHU| 1E ET AL 2,956,639

COKE: OVEN GAS NAPHTHALENE ABSORBING FINAL COOLER 2 Sheets-S'heet 2Filed Jan. 22, 1959 T w mk TWK) G UNH 9 OAA 1 RMT( m 5 5 c. G m N 1mm@NTT( T 4 M U S D O o A2a mn W s 'Nw G QH A IL G L their' e? Trae/ Y'United States COKE OVEN GAS NAPHTHA-LENE ABSORBING FINAL COOLER ElwoodV. Schulte and Harold T. Stirling, Pittsburgh,

Pa., assignors to Koppers Company, Inc., a corporaon of Delaware FiledJan. 22, 1959, Ser. N0. 788,361

15 Claims. (Cl. 18`3-.2)

This invention -relates to improvements in the general operation offinal cooler apparatus for coke oven chemical recovery plants, and moreparticularly, to improvements in the operation of such final coolers ofthe general type comprising a towerhaving an upper gas washing isectionand a lower water scrubbing section with a .funnel immediately below thevlower gas inlet to collect the cooling Water from the washing sectionand a depending -tail pipe, to discharge the water into a bath ofsolvent for naphthalene, such as tar, at the base of the scrubbingsection, with zig-zag horizontal baffles between the base of the tailpipe and the apex of the cone of the .funnel :for decantation of thewater before it overflows at a-level below the top of the funnel to awater cooler Vfor return to the upper part of the gas -washing sectionof the tower. In such apparatus, tar is fed to the base of the lowerscrubbing section, continuously at about .the level of the second bottombaffle, and intermittently at higher levels, and mechanical means areprovided for off-flow of tar from the base of the lower scrubbingsection=to maintain a constant level of the bath of solvent, such astar, to absorb naphthalene which has condensed from the gas by thecooling water, to remove such naphthalene prior to flow of the water tothe water cooler on its way back to the upper gas cooling section in theVof the scrubbed water in the scrubbing section, during its flow to thewater cooler, than the scrubbing section is normally designed tooperate, without increasing the -height of the section and tower orrequiring supplemental decantation equipment outside the tower in thelimited ground area around the same for the purpose.

More specifically, a primary object of the invention is to effect suchchange in mode of operaion in a simple, economical and facile wayrequiring no additional equipment by altering the arrangement andlocation of the parts, in a manner equally adaptable to static typefinal coolers of the packed type and to all spray type coolers devoid ofpacking in the gas cooling section and operable with water pressurehigher than customary with the packed column type cooler.

Accordingly, the invention comprises lowering the location of the funnelin the existing coolers, as well as new ones, and raising the wateroutlet to maintain below the gas inlet a head of the hot cooling wateron the tail pipe at a levelat least as high as the top of the funnel,and preferably, at a distance above the top of the funnel equal tothe-height of two of the lower bafiies, disposing three of the upperbaliles to serve as foam collectors beneath their lower surfaces, andventing the three upper bandes, of a vertical row of baffles of greaterheight VVthan the overall horizontal dimension ofthe baffles, `to thegas space in the upper gas cooling section vof the tower. Preferably,the upper three bafes are oppositely inclined, but they may behorizontal instead ywhen provided with a deep weir lip.

Preferably, eachrof the lower baffles `are also provided with solventdrains to the bath below, and forall Vspray coolers a perimetrical ringis superposed abovethe perimeter of va conical Ydeliector below the gasinlet to deaerate the water passing to the head of water above ythe tailpipe. Y

The standard methodis to spray water into a tower in the form of an allspray section or a packed column, through which the gas passes from theexit of the arnmonia saturator to the benzol or light oil scrubber. Thepurpose of this final cooler is to removethe heatlthat had been formeddue to the compression of the gas at the exhauster before the reheaterforthe saturatonand also to remove the heat'formed d ue tothe reactionofvsulfuric acid with ammonia in the saturator. The temperature of the gasleaving-thews'aturator is lowered as muchfas possible with coolingwateravailable at the plantlo obtain maximum absorption oflight oil ,fromYthe,gas in the benzol washers using the minimum vof lwash oil circulation.4In this type of final cooler the water isvsprayed `into the upper YgasVcooling section 'where it contactsY the gas countercurrently to removethe heat from the gas. The gas, in being cooled at the final cooler,frequently reduces the dewpoint of the naphthalene in the gas to a pointlower than the dewpoint ofthe naphthalene in the gas leaving the primarycoolers. Experience also indicates that the gas leaving the primarycoolers frequently has a naphthalene content greater than that whichwould be present in the gas if itwas merely saturated to its dewpoint.Naphthalene, therefore, that is .condensed out of the gas, is washedwith the water out of the base of the lupper final cooler lsection -andinto a lower scrubbing section where the naphthalene is recovered by asolvent. The water is then pumped Yto the cooling vtower where itisren-cooled in preparation for recirculation back tothe upper finalcooler section again.

In this lower scrubbing section, the water from the bottom of the uppergas coolingsection of the final cooler flows through a funnel into atail pipe downwardly to a pointnear the base of the lower `section ofthe tower located below the upper final gas cooling section. Below thetail pipe or downspouty a baffle defiects the water and causes it toturn upwardly to a point near the top of the tail pipe inthe lowernaphthalene absorbing or scrubbing section. Located above the base ofthe tail pipe, nine zig-zag horizontal baffle plates with openings attheir ends alternating from side to side, direct the water horizontallyback and forth as it passes between .the trays or baflies progressivelyupwardly to a wateroverflow at the level of the top of the tail pipe inthe lower naphthalene absorbing vor scrubbing section. The opening atthe end of each tray represents roughly 10% of thetotal cross-sectionalarea of the shell. The distance between traysis usually about two feetand the velocity of the water, as it ows betweentrays, is in theneighborhood of ten times the superficial upward velocity in thenaphthalene absorbing section. The superficial upward velocity is thatvelocity that would exist if thewater had moved uniformly upwardlythrough the tower when it was not equipped with any obstruction of anykind.

Coke oven tar is either fed continuously or batchwise to the lowernaphthalene absorbing section and a tar level maintained a few feetabove the bottom of the tail pipe. A heating coil submerged in the tarat the base of the lower naphthalene absorbing section keeps the tar atabout 60-95 and assist in preventing emulsions.

The water, as it departs from the base of the tail pipe, ows upwardlythrough the bath of tar, and in doing so, loses its entrainednaphthalene to the tar. The naphthalene dissolves in the tar. Thede-naphthalenized water then overflows from a level below the top of thefunnel at the top of the tail pipe in the naphthalene absorbing section,as described previously, to a hot well where conveniently it is removedby pump and delivered to the cooling tower to re-cool the water inpreparation for additional cooling in the upper final cooler section.Experience over the years, and up until about the time of thisinvention, has been that this particular design of the lower naphthaleneabsorbing or scrubbing section was limited with regard to water rate tothe extent that the nominal or superficial velocity upwardly of thewater above the tar level in the lower naphthalene absorbing sectioncould rarely exceed about A@ to W10 of a foot per minute withoutcarrying tar out of the naphthalenc absorbing section. Tar entrainmentin the outlet water from this lower section is impractical orintolerable, and undesirable, because this tar, when it is exposed toair in the cooling tower, becomes oxidized and cooled and therebydeposits on the surfaces of the packing in the cooling tower.Eventually, these surfaces become so badly contaminated that the coolingtower must be taken out of service and cleaned. This is a troublesomeand expensive procedure and it is apparent that it should be avoided, ifpossible.

In such conventional system the trays originally were equipped with alarge number of perforations, about 5/16 diameter on 4" centers, and asa naphthalene absorber remains in service for a period of years, itbecomes necessary to reduce very gradually the water rate that is passedthrough the naphthalene absorbing section in order to prevent carry-overof tar out of the section. Over the years, a pitch-like depositaccumulates, as a result of continuous operation, on each of thehorizontal trays located in the lower naphthalene absorber section, sothat the free area between trays became reduced. This results in agradual increase in water velocity between trays to the extent tha-t theheavier tar is carried across and upwardly with the water to the outlet.Removing the pitchdlike deposits from the trays would restore thecapacity of the unit from .the standpoint of tar separation from waterto that which existed when the unit is first placed in operation.Enlargement of the perforations in the trays to approximately 11/2diameter, in order to keep the trays clean, indicates that the capacityof the lower naphthalene absorbing section, from the standpoint of tarseparation from water, was no more, and perhaps less, than it had beenbefore the holes in the trays were enlarged. In order to attempt toincrease the capacity of the lower naphthalene absorbing sections, otherschemes were also tried. These included increasing fthe free area of theopening at the ends of each of the trays, adding tar intermittently,adding tar to the naphthalene absorbing sect1on at slower rates,eliminating perforations entirely from each of the trays and installingindividual tray drains that carried the separated tar either to the traybelow or directly to the tar located at the base of the lowernaphthalene absorbing section. The experience from each of these changesin design was that the attempt to increase the capacity of the unitfailed and that the superficial velocity of the water upwardly throughthe lower naphthalene absorbing section could not be increased muchabove the 5A() to %0 of a foot per minute cited previously in thisconnection.

The present inventors conceived that very likely one of the limitingfactors in the capacity of these units was associated with theentrainment of tine gas bubbles in the water that was passing from theupper final cooler sect-ion down through the tail pipe and up throughthe tar in the lower scrubbing section. It was felt that any minute gasparticles would cause a frothing action as the gas and water mixturechanged direction at the base of the `downcomer or tail pipe and passedupwardly through the tar solvent. Such gas particles would entrain tarand carry the tar upwardly to the top of the lower naphthalene absorbingor scrubbing section because of the fact that the presence of the gas inthe tar would lower the average specic gravity of that particularmixture below the specific gravity of the water.

Test work and observations demonstrated `that this conception regardinggas entrainment and its etect upon the capacity of the column wascorrect. The tests demonstrated 'that when a small amount of air or gaswas entrained in the water passing downwardly through the tail pipe fromthe funnel and up through a layer of tar in the lower naphthaleneabsorber section, the allowable superficial velocity of water was about5A@ to %0 of a foot per minute which was very much like the conditionsfound inpractice in final cooler systems in coke plants. In other tests,with complete removal of air or gas from the water before it passes fromthe funnel down into the tail pipe and then upwardly through the tarlayer, the present inventors were able to obtain superficial velocitiesof at least two feet per minute without entrainment of tar in that wateras the water exited from the lower absorber section. To this end, theinventors lower the funnel and raise the water level outlet of the unitin the lower section to form a hold tank above the funnel, whereby thewater, before it leaves the gas liquid con tacting upper section of thefinal cooler, is given a retention time at low velocity, while stillabove the base of the funnel, of at least more than ten seconds andusually not more than three minutes to ailow a major portion of theentrained gas to be separated by gravitational separation from the waterbefore this water passes into and suddenly tlows down at a much highervelocity through the tail pipe or downcomer, for contact with the tar inthe lower naphthalene absorbing section, which very high velocityprevents residual gas from escaping to the head of the column of waterby gravitational separation.

The inventors further found that the capacity of the lower naphthaleneabsorbing section could be further increased above that of previouslydesigned units even if there still was some entrained gas or air in thewater by entrapping the particles of the water that had the residual gasentrained therein, from the water, after it leaves the tail pipe, in amanner that they would not be allowed to reach the surface of the waterbelow the funnel where the water flows out from the lower naphthaleneabsorber or scrubbing section of the final cooler to pass on to thewater cooler. A sloping type of upper baffle has been found to be asimple means for the entrapment of these tar particles which have agravity less than that of water due to the presence of the residual gasor air particles therein. However, there lare other simple means thatare effective for the entrapment without departure from the principleused. For example, the entrapping upper baiiies are suitable when placedhorizontally with a downwardly extending tlip at the edge of the baiiieadjacent the opening opposite this baffle. Also, the sloping upper batheeffect is obtained by building the baflie segments in horizontal steps,working downwardly stepwise to a point adjacent the opening.

The function of the upper entrapment bafes, of course, is not completedif the entrapped gas and its entrained tar are not allowed to escapefrom a point below said baffle and, therefore, vents are included as anescape mechanism to remove either separated and unseparated gas asrapidly as it accumulates. The capacity of the lower naphthaleneabsorbing section of the nal cooler is thus increased from thestandpoint of separating tar from water flowing through rthe lowernaphthalene absorbing section after said water has been in contact withsaid tar and while there is entrained gas or air in 4the water as itleaves the downcomer or tail pipe and enters the tar submerging thebottom of the tail pipe. It is now possible to obtain tar free water atvelocity capacities greater than those obtainable previously in spite ofthe fact that some gas or air may be entrained in the water.

The entrainment problem is not as serious with final coolers designedwith -a contact surface made up of packing in lthe upper cooler section,as it is with the all spray type of gas cooler. When water is sprayedonto the surface of the packing at or near the top of the upper finalcooler section, this water drains gently over the surface of the packinguntil it reaches the lowerrnost portion of the packing. From here itdrops gently onto the surface of the water retained in the funnel ofthis type of cooler. Unfortunately, a packing is somewhat limited incapacity and greater gas velocities can be tolerated in the final coolerwhile obtaining satisfactory heat transfer by the use of an all sprayupper section devoid of packing to create the surface required totransfer heat from the gas to the water. In this case, a plurality ofsprays is used at one or more elevations in the upper cooller section.When spraying the water with differential pressures in excess of 3 or 41lbs./sq. in. across the spray nozzles and spraying the water downwardlyinto the tower, the spray droplets -impinge against the surface of thewater at the base of the upper final cooler section at relatively highvelocity. This rapid impingement aggravates the de-entrainment problemat the base of the upper cooler section and a greater retention time isthereby required in order to get the gas particles separated from thehold tank of Water at the head of the tail pipe.

This disadvantage of `an all spray type gas cooling upper section incombination with a lower naphthalene absorber section for purposes ofremoving naphthalene from the hot cooling water, is overcome here by theraised water level arrangement so as to operate the upper gas finalcooler section with gas velocities in excess of one foot per secondupwardly through the upper gas cooling section and with use of therequired amount of water to obtain the desired cooling of the gas andstill obtain superficial water velocities upwardly in the lowernaphthalene absorber section greater than 0.5 foot per minute.

We have also overcome and minimized still further the effect of thespray impinging against the surface of the water bath by placing aconical baffle above the top level of the hold water retained in thefunnel in the lower section of the final cooler with a perimetricaldefiector ring above the perimeter of the conical bafiie, so that thespray now impinges against this bafe to deaerate the liquid before itreaches Contact with the hold water in the funnel. This has also made itpossible to increase the capacity of the lower naphthalene absorbingsection even with the all spray type upper gas cooling section.

While the invention as hereinabove set forth is primarily designed for,and particularly adapted to improve the general operation of, a cokeoven gas final cooler of the special types set forth, without increasingthe overall height of the tower or its lower water scrubbing solventsection, and without requiring location of auxiliary equipment aroundthe ground area alongside the tower or its water cooler, to complete4the de-tarring of the water before it enters the water cooler forreturn to the upper gas washing section, the invention is not limited inall its aspects to such specific embodiment of the invention, since muchof the advantages of the invention is of utility in other countercurrentscrubbing, decanting, and emulsion separating operations and processesinvolving chambers containing gas in contact with aqueous mediumsrequiring separation of two immiscible mediums of different specific.gravities. Hence, the invention, in its broader aspects, is not confinedin all its uses to the specific use and specific embodimentherein-described and illustrated.

In addition to the general objects recited above, the invention has forfurther objects such other improvements or advantages as may be found toobtain in the structure and general operation of a final cooler in acoke oven gas chemical -recovery system as shown on the drawings andhereinafter-described or claimed.

In the accompanying drawings:

Figure l is a schematic side elevational arrangement of a train ofapparatus elements for processing coke oven gas to remove benzoltherefrom which includes the present invention therein;

Figure 2 is a schematic vertical cross-section of the final coolertherein, with the upper gas cooling section in the form of an all spraychamber devoid of packing;

Figure 3 is a horizontal sectional View taken on the line III-III ofFigure 2;

Figure 4 is a partial view of the upper portion of Figure 2, but withthe upper gas cooling section in the form of a packed column with spraysto deliver the cooling water to the top of the packing for tricklingthrough the same to the lower water scrubbing section.

The same reference numerals are used for like parts in each of theseveral views.

Referring to the drawings, there is indicated at 10 a coke oven battery,from which coke oven gas is derived, and which passes out th-rough thecollecting main 11 to a downcomer 12, for tar and aqueous condensate ofthe gas, and thence, through a line 13 to the primary cooler 14, throughwhich the gas passes countercurrently to cooling water from lines 16,and thence is forwarded by exhauster 17 to a combined tar precipitatorand reheater 18. In the primary cooler 14 the gas is cooled to about 25C., and tar and ammonia liquor therefrom are drained to the hot draindecanter tank 19 which discharges the tar to the tar storage tank 2t)and overows ammonia liquor through line 21.

The gas from the exhauster 17 enters the tar extractor 1S at about 30 C.from the reheater therein, and leaves at the same temperature to enterthe ammonia removal means in the form of a saturator 22 at said 30 C.temperature. In the saturator the ammonia of the gas reacts withsulfuric acid to form ammonium sulfate which precipitates therein, thewater of crystallization passing ofi with the gas at a slightly highertemperature as a result of the reaction. From the saturator 22 the hotgas passes to an acid separator 15 which removes any adhering acid.

As the gas to be debenzolized should be at a lower temperature for thispurpose, the gas then passes into a final cooler 23 through the gasinlet line 24, and the cooled gas leaves through the gas outlet line 26to enter the light oil, or benzol, scrubber 27 wherein the gas isscrubbed with wash oil to absorb the light oil, i.e., benzene and itsho-mologues, etc. From the benzol scrubber the gas is lead to furthergas processing equipment, or use, or to a gas holder for furtherservice.

in the final cooler 23, the upper section of the tower is given over todirect gas washing with cold water which enters through spray heads 25from a water cooler 25. The gas leaves at the upper end of the tower andenters at the intermediate level of inlet 24.

As shown in Figure 2, the upper gas cooling section 23a is devoid ofpacking and the gas is washed by sprays of water under higher pressurethan when a packing 23h is used as shown in Figure 4.

Referring to Figure 2, for the all spray type cooler, a conicaldefiector 27 is disposed across the tower 23 immediately below the gasinlet 24, with a peripheral space 28 between the same and the verticalwall ofthe tower 23, and downwardly extending deliector ring tray 2,9 issuperposed over the defiector 27 above the space 28 to arrest the sprayfrom the spray heads 25 before the liquid of the spray passes throughsaid space 28, thus deaerating the spray liquid of some of the cokeovengas ,and of any carryover air from the air cooled water cooler ,25.

A funnel 33 is located below the deflector 27 with the top 30 of thefunnel at a distance below the defiector, which distance is about equalto the height of three of the horizontal zing-zag baille spaces abovethe top level 31 for a tar bath at the bottom of the lowernaphthaleneabsorption water-scrubbing section 23C in the lower part ofthe final cooler tower 23. A tail pipe 32, disposed axially of the tower23, leads from bottom 4outlet 34 for the funnel 33 to terminate abovethe lowermost of a series of horizontal zig-zag baiiles 35 below, whichare spaced about 2 feet apart, one above another. The bottom tray is setabout six feet above the bottom or base of the lower scrubbing section,and the zig-zag baffles are in a vertical row or series of livehorizontal lower baffles and three upper oppositely inclined baies 36,with the fixed closed end of these baffles raised about an inch abovetheir free open ends 37 to provide a foam collecting area 38.

The free ends 37 of the inclined bafes 36 are provided with dependinglips 39 to act as weirs, each of which is spaced the same distance,about 2 feet, above a tray below, which is the same spacing as thespaces between the horizontal trays lower down in the lower waterscrubbing section 23C. The foam areas 38 are lvented to the gas space23a above in the upper gas cooling section at a level just below the gasinlet 24 to the upper gas cooling section 23a by vents 40, and theinclined bafes 36 range -up to the level of the top of the tail pipe 32,which is the level of the outlet from the funnel 33.

The lower horizontal bales or trays are each provided with tar retaininglips 41 and tar drains 42.

The scrubber water is taken o from the lower scrubbing section 23e by aliquid outlet 43, located above the top of the tail pipe 32, just belowthe top perimeter of the funnel 33, by means of an adjustable over-nowmechanism 47 set to maintain a water liquid level in the lower scrubbersection at a level above the top perimeter of the funnel 33 and justbelow the gas inlet 24 to the upper gas cooling section 23a of the tinalcooler. This overflow level controller 47 is vented by a line 48 to anemergency water over-flow line 49 leading from a higher level above thefunnel 33 in the `water scrubbing section 23C.

Tar from the tar storage tank 20 is fed as solvent into the lower waterscrubbing section by automatic means therefor 50, continuously at yalowermost level 51, preferably at the level of the second tray 35 from`the bottom, and intermittently at several higher levels 52 to wash downnaphthalene accumulations.

The tar is withdrawn from the base or bottom of the lower scrubbingsection 23C through a tar outlet 53 by automat-ic decanter meansoperable to maintain the bath or pool of tar at a constant level,submerging the lower end of the tail pipe 32, at `about the level of thesecond tray 35 from the bottom of the scrubbing section 23C.

As shown, this automatic decanter means comprises a riser line 54 whichleads to the bottom of an inner tube 55 open at its top to an outerconduit 56. The tar is returned 4to the tar decanter tank 19 by a line57 leading from the bottom of the outer conduit 56.

The tar which is released of gas in the vents 4t) is drained to theouter conduit 56 by means of drain lines 58. The level of the tar bathis controlled by a tar regulator 59 vented at 6@ to the upper gascooling section 23a. As conventional, the tar is heated by means, notshown, to keep it fluid.

The structure and operation is .the same with the tower constituted of apacking, as in Figure 4, except that as the cooling water merelytrickles on the head of the hold tank of water which is above thefunnel, the conical deector 27 and ring 29 are eliminated as unnecessaryWith Water merely tckling down from the packing 231:.

In the table below, are the operating data with the unit arranged as inFigure 2.

TABLE Operating data-five horizontal `trays, three sloping trays,sprayed water feed with feed hold-up tank Run No 17 18 19 20 Water Rate,gpm 70 88. 5 129 97 Superficial Water Velocity, ft./

Min 0. 97 1. 23 1. 79 1. 35 Tar Rate, g D mA 2% 2% 2% 2% Tar Level,Trays. 3 3 3 3 Water Inlet Temp., O-. 32 38 40 42 Tar Inlet Temp., C96.1 98. 9 96. 6 93. 4 Temp. Bet. 1st and 2nd Tr.,

C 53 45 45 45. 5 Top Condition Excellent Good B ad Passable Moisture inTar Foam =25.1- by weight The top surface was in excellent conditionduring run No. 17 when the superficial velocity was about 0.97 foot perminute. Run No. 18, during which the supercial velocity was 1.23 feetper minute, had a faint trace of fine froth on the top surface. A veryoccasional group of bubbles rose through the No. 1 vent. However, thesurface conditions in this run were good and appeared to be better thanthey had been in run No. 14, when there was no hold tank and thesuperficial velocity was only 1.12 feet per minute.

The superficial velocity was increased to 1.79 feet per minute in runNo. 19. A considerable amount of ne froth began to accumulate on thesurface which would not in itself have been serious. However, there wereseveral large patches of tar and air which iioated up making the rundenitely not passable. Tar foam began to flow from the No. l vent to thedrum. However, the foam over-W rate was only about half as fast as ithad been in a run when there was no hold-up tank and the supercialvelocity was only 1.42 feet per minute. There was about two inches oftar foam in the No. 2 vent and an occasional bubble in the No. 3 vent.

The water rate was decreased in run No. 2O until the superficialvelocity was 1.35 feet per minute. The top conditions were definitelypassable. A slight stream of tar flowed from the No. l vent, and theconditions in the Nos. 2 and 3 vents remained about the same. This is animprovement in passable water rate over that in a run during which therewas no inlet hold tank and the supercial water velocity was only 1.12feet per minute. It is also a great improvement over operation withhorizontal trays when the maximum tolerable supercial velocity was onlyabout half as much.

After the completion of run No. 20 the splash plate and ring baille wereremoved. The top conditions became much worse showing that a largeamount of the air entrainment is relieved when `the impingement of thespray on the water surface is stopped.

In operation with the water spray from the all spray chamber 23a trainedon the ring deector 29 and conical deflector 28, the quantity of gasentra-inment is initially appreciably decreased by said deectors and isthen further decreased by the hold tank body of water when retained inthe funnel 29 above the top of the tail pipe 32. With the three vented,generally horizontal slanted trays above the live truly horizontaltrays, it is possible to operate at supercial upward velocities as highas 1.12 feet per minute without the hold tank of water and 1.35 feet perminute with the hold tank of water.

The water is retained at such a low velocity in the hold tank that mostof the entrained gas rises to the surface and passes into the gas streamabove. In the tail pipe the velocity is at a rate that the residualentrained gas cannot pass up but passes on through the bath of solventat `the base of the tail pipe.

In the solvent bath the naphhalene is absorbed from the water and in sodoing, some tar picks up some of the entrained gas from the water andforms globules lighter than the solvent and water. As the hot coolingwater traverses the zig-zag pathway horizontally, the tar which hasentrained gas rises to the bottom surface of the trays as the water owshorizontally along the bales. The tar which releases the entrained gassettles back down to the top surface of `a tray below and thence passesthrough the drains to the bath of solvent below. Tar globules andreleased gas nally rise to the collecting areas below the inclinedbaflies, enter the vents at a water level below the upper outlet for thescrubbed water. The water thus leaves the scrubbing section free ofcarryover tar solvent and naphthalene, and the lighter tar and gas risethrough the vents releasing the gas into the gas cooling section at alevel above the water outlet. As the tar is released of its entrainedgas it settles in the vents to ow oi through the tar drains to the taroiftake means.

In typical operation, tar is continuously added opposite the No. 2 trayfrom the bottom at a rate between one gallon of tar per ton of coalcarbo-nized per day and about gallons of tar per ton of coal carbonizedper day. The tar can also be added intermittently instead ofcontinuously.

The invention as hereinabove set forth in embodied in particular formsof construction and method of operation, but may be variously embodiedwithin the scope of the claims hereinafter made.

We claim:

l. Final cooler apparatus for coke oven gas chemical recovery plantscomprising: `a tower constituted of an upper gas cooling section havingan intermediate gas inlet to the tower in communicable connection withan ammonia saturator, an upper youtlet for finally cooled gas from thetower in communicable connection with a light oil scrubber for the cokeoven gas, and means for introducing cooling water to the upper portionof said upper section, and a lower water scrubbing section having itstop below said gas inlet and in open communication with the base of theupper section of said tower to receive hot cooling water therefrom, afunnel in said lower section with its top perimeter at a spaced distancebelow said gas inlet, a tail pipe disposed axially of said tower andextending from the outlet of said funnel down to a spaced distance abovethe base of the lower section, a vertical series of horizontal zig-zagflow baffles of greater height than the horizontal dimensions of thelower section disposed in the lower section to range upwardly from belowthe base of the tail pipe to the top thereof around the outside of thetail pipe, the upper baffles I of the series being disposed to serve asfoam collectors beneath their under surfaces and having vents therefromto the gas cooling section above the funnel, a water outlet from saidlower section at a level above the uppermost of the vertical series ofbaiies but below the underside of said funnel, conduit means for outflowof water from the Water outlet with provision for maintaining a waterliquid level in said lower section at a level above the top perimeter ofthe funnel and below said gas inlet, a water cooler connected with saidwater outlet for cooling tne water from said conduit means and providedwith means for returning the cooled water back to the means forintroducing cooling water to the upper section of the final cooler,means for introducing solvent of a different specific gravity from waterinto the lower section, means for draining solvent from the lowerbaffles of the series to the base of the lower section at a level whichis below the lowermost baffles below the base of the tail pipe, andoutlet means for offtake of the drained solvent from the base of thelower section with provision to maintain a bath of the solvent aroundthe base of said tail pipe.

2. Apparatus as claimed in claim l, and in which the upper baffles,which are disposed to serve as foam co1- assenso lectors, compriseoppositely inclined baies with their lower free ends spaced the samedistance above a baille below, which is the same as the distance betweenthe lower baffles with the solvent drains, and in which each vent isprovided with a drain for flow of solvent -to the outlet means forofftake of solvent from the base of the lower section.

3. Apparatus as claimed in claim 1, and in which the upper gas coolingsection is one of the all spray type devoid of packing and in which aconical deector and a superposed perimetrical ring deector is interposedat a level between the gas inlet to the gas cooling section and thelevel for the top of the liquid above the tail pipe in the lower waterscrubbing section.

4. Apparatus as claimed in claim l, and in which the upper gas coolingsection is one of the packed type containing water and gas dispersingcontact material between the gas inlet and the water inlet to the uppersection, and in which the chamber area between the base of the packingand the level for the top of the liquid in the lower water scrub-bingsection is devoid of obstructions to the downflow of liquid.

5. Final cooler apparatus for coke oven gas chemical recovery plantscomprising: a tower constituted of an upper gas cooling section havingan intermediate gas inlet to the tower in communicable connection withan ammonia removal means, an upper outlet for iinally cooled gas fromthe tower in communicable connection with a light oil scrubber for -thecoke oven gas, and means for introducing cooling water to the upperportion of said upper section, and a lower water scrubbing sectionhaving its top below said gas inlet and in open communication with thebase of the upper section of said tower to receive hot cooling watertherefrom, a funnel in said lower section with its top perimeter at aspaced distance ybelow said gas inlet, a tail pipe disposed axially ofsaid tower and extending from the outlet of said funnel down to a spaceddistance above the base of the lower section, a vertical series ofhorizontal zig-zag ow baflies of greater height than the horizontaldimensions of .t-he lower section disposed in the lower section to rangeupwardly from below the base of the tail pipe to the top thereof aroundthe outside of the tail pipe, the -upper baffles of the series beingldisposed to serve as foam collectors beneath their under surfaces andhaving vents therefrom to the gas cooling section above the funnel, awater outlet from said lower section at a level above the uppermost ofthe Vertical series of baffles but below the underside of said funnel,conduit means for outow of water from the water outlet with provisionfor maintaining a water liquid level in said lower section, a watercooler connected with said water outlet for cooling -the water from saidconduit means and provided with means for returning the cooled waterback to the means for introducing cooling water to the upper section ofthe nal cooler, means for introducing solvent of a different specificgravity from water into the lower section, means for draining solventfrom the bathes of the series to the base of the lower section below thebase of the tail pipe, and overflow outlet means for offtake of thedrained solvent from the base of the lower section with provision tomaintain a bath of the solvent submerging the base of said tail pipe butbelow said water outlet.

6. Apparatus as claimed in claim 5, and in which the upper baffles whichare disposed to serve as foam collectors, comprise opposi-tely inclinedbaflies with their lower free ends spaced the same distance above abaille below, which is the same as the distance between the lower baieswith the solvent drains, and in which each vent is provided with a drain-for ilow of solvent to the outlet means for ofltake of solvent from thebase of the lower section.

7. Final cooler apparatus for coke oven gas chemical recovery plantscomprising: a tower constituted of an upper gas cooling section havingan intermediate gas inlet to the tower, an upper -outlet for finallycooled gas from.

,the tower, and means for introducing cooling water to the upper portionof said upper section, and a lower water scrubbing section having itstop below said gas inlet and in open communication with the base of theupper section of said tower to receive hot cooling water therefrom, afunnel in said lower section with its top perimeter at a spaced distancebelow said gas inlet, a tail pipe disposed axially of said tower andextending from the outlet of said funnel down to a spaced distance abovethe base of `the lower section, a vertical series of horizontal zig-zagow bafes of greater height than the horizontal dimensions of the lowersection disposed n the lower section to range upwardly from below thebase of the tail pipe to -the top thereof around the outside of the tailpipe, the bai-lies of the series being disposed to serve as foamcollectors beneath their under surfaces and having vents therefrom tothe gas cooling section above the funnel, a Water outlet from said lowersection at a level above the uppermost of the vertical series of baflesbut below the underside of said funnel, conduit means for outflow ofwater from the water outlet with provision for maintaining a waterliquid level in said lower section at a level above the top perimeter ofthe funnel and below said gas inlet, means for introducing solvent of adifferent specific gravity from water into the lower section, andoverflow outlet means for oiftake of solvent from the base of the lowersection with provision to maintain a bath of the solvent submerging thebase of said tail pipe but below said water outlet.

8. Apparatus as claimed in claim 7, and in which the upper baflies,which are disposed to serve as foam collectors, comprise oppositelyinclined baffles with their llower free ends spaced the same distanceabove a bale below, which is the same as the distance lbetween the lowerbaffles with the solvent drains, and in which each vent is provided witha drain for flow of solvent to the overow outlet means for oitake ofsolvent from the base of lower section.

9. Apparatus as claimed in claim 7, and in which the upper gas coolingsection is one of the all spray type devoid of packing and in which aconical deector and a superposed perimetrical ring deflector isinterposed at a 'level between the gas inlet to the gas cooling sectionand the level for the top of the liquid above the tail pipe in the lowerwater scrubbing section.

10. Final cooler apparatus, comprising: a water scrub- Lbing sectionhaving at its top a water inlet to receive water containing gas and aWater immiscible constituent, a funnel in said scrubbing section withits top perimeter at a spaced distance below said water inlet, a tailpipe disposed axially of said funnel and extending from the outletthereof down to a spaced distance above the base of said scrubbingsection, a vertical series of horizontal zig-zag ilow bailles of greaterheight than the overall horizontal dimension of the scrubbing sectiondisposed in the latter to range upwardly from below the base of the tailpipe to the top thereof around the outside of the tail pipe, the upperbaies of said series being disposed to serve as foam collectors beneaththeir undersurfaces and having lvents therefrom to a gaseous area at alevel above the water inlet, a water outlet from said scrubbing sectionat a level above the uppermost of the vertical series of baies but belowthe underside of the funnel, conduit means for voutiiow of water fromthe water outlet with provision for maintaining a water liquid levelabove the top perimeter of the funnel and below said water inlet, meansfor introducing a solvent of greater specific gravity than water andimmiscible therewith into the scrubbing section, means for drainingsolvent from the lower bales of said series to a point below the base ofthe tail pipe, and overflow means for offtake of solvent from the baseof said scrubbing section at a level below the base of the tail pipewith provision for maintaining a bath of solvent submerging the base ofsaid tail pipe but below said water outlet.

1l. Apparatus as claimed in claim l0, and in which the upper baies,which are disposed to serve as foam col lectors, comprise oppositelyinclined baflles with their lower free ends spaced the same distanceabove a balile below, which is the same as the distance between thelowermost bafes with the solvent drains, and in which each vent isprovided with a drain for ow of solvent to the overow outlet means forsolvent from the base of the lower section.

12. Apparatus as claimed in claim 10, and in which a conical detlectorand a superposed perimetrical ring deiiector is interposed at a levelbetween the water inlet and the level for the top of the liquid abovethe tail pipe in the scrubbing section.

13. Apparatus for separating naphthalene from water containing entrainedgas, comprising: a water scrubbing section having at its top a waterinlet to receive water containing gas and water immiscible naphthalene,a funnel in said scrubbing section with its top perimeter at a spaceddistance below said water inlet, a tail pipe disposed axially of saidfunnel and extending from the outlet thereof down to a spaced distanceabove the base of said scrubbing section, a vertical series ofhorizontal zigzag flow batlies disposed in the scrubbing section torange upwardly from below the base of the tail pipe to the top thereofaround the outside of the tail pipe, a water outlet from said scrubbingsection at a level above the uppermost baie but below the underside ofthe funnel, conduit means for outflow of water from the water outletwith provision for maintaining a water liquid level above the top of theperimeter of the funnel and below said water inlet, means forintroducing a liquid solvent for naphthalene of greater specific gravitythan, and immiscible with, water into the scrubbing section, and overowmeans for offtake of solvent from the base of said scrubbing section ata level below the base of the tail pipe with provision for maintaining abath of the solvent submerging the base of said tail pipe but below saidwater outlet.

14. Apparatus for separating naphthalene from water containing entrainedgas, comprising: a water scrubbing section having at its top a waterinlet to receive water containing gas and water immiscible naphthalene,a funnel in said scrubbing section with its top perimeter below saidwater inlet, a tail pipe disposed axially of said funnel and extendingfrom the outlet thereof down to a spaced distance above the base of saidscrubbing section, a vertical series of horizontal zig-zag flow passagesdisposed in the scrubbing section to range upwardly from below the baseof the tail pipe to the top thereof around the outside of the tail pipe,said series of baies being of greater height than the overall horizontaldimension of the water scrubbing section and having the upper batflesdisposed to serve as foam collectors beneath their undersides andprovided with vents therefrom to a gaseous area at a level above thewater level of the scrubbing section, and the lower bafes of the seriesof bales having drains for draining solvent directly to a level in thebase of the scrubber below the base of the tail pipe, a water outletfrom said scrubbing section at a level above the uppermost bathe of theseries thereof but below the underside of the funnel, conduit means foroutflow of water from the water outlet with provision for maintainingwater in the scrubber at a level above the uppermost 'bal-lie of saidseries thereof, means for introducing a liquid solvent for naphthaleneof greater speciic gravity than and immisci ble with water into thescrubbing section, and outlet means for Gif-take of the drained solventfrom the base of the scrubber with provision for maintaining a bathlevel of the solvent for submerging the base of said tail pipe with thetop level of t-he bath below said water outlet.

l5. A method of scrubbing final cooler water from coke oven gas plantsto remove naphthalene therefrom, comprising: continuously accumulatingfinal cooler water aforesaid as a body of water gravitationallydescending in a funnel to a tail pipe therefor and retained at lowvelocity of flow above said tail pipe for a time to allow a majorportion of the entrained gas to gravitate upwardly out of the bodybefore the water enters the tail pipe, owing the water from the body athigher velocity through the tail pipe into a bath of solvent fornaphthalene that is immiscible with and of greater specific gravity thanwater at the base of said tail pipe, to leave the naphthalene of thewater in the solvent, owing the water upwardly for outflow of the wateraround the tail pipe to an upper level, above the top of the tail pipebut below the funnel through a series of horizontal zig-zag ow paths ata velocity in each horizontal ow path greatly in excess of thesuperficial upward Velocity to said upper level, draining solvent fromeach of a plurality of the lower horizontal ow paths to the bath of sol-15 vent below, and entrapping escaping gas and lighter globules ofsolvent containing entrained gas at the top of the upper horizontal flowpaths and venting said gas to a gaseous area outside said water area toprevent the gas and lighter solvent from reaching the upper level abovethe top of the tail pipe for outow of the water, feeding solvent to, andwithdrawing solvent from, the bath to maintain the bath of the solventat a level for submerging the base of the tail pipe with the top levelof the bath of solvent below said upper level above the top of the tailpipe for outflow of water, and withdrawing the water at the upper levelfor outow of water in a manner to maintain a body of water in the funnelat a level above the top of the tail pipe as aforesaid.

References Cited in the file of this patent UNITED STATES PATENTS2,776,021 Van Ackeren Ian. 1, 1957 2,810,450 Hartmann Oct. 22, 19572,887,174 Ray May 19, 1959

